Joe Manganiello was nervous before proposing to Sofia Vergara

The 'Magic Mike' actor, who got engaged to the 'Modern Family' actress in Kauai over Christmas after six-months of dating, reportedly didn't want to pop the question in a public setting at the St. Regis Hotel in Princeville just in case she said no.

A source said: "He said he wanted to keep it private just in case she didn't say yes. It actually didn't seem like he was joking about that. He did seem genuinely nervous that maybe this wasn't going to go well. He said this was a once-in-a-lifetime opportunity with a one-in-a-million woman."

The 38-year-old heartthrob spent weeks planning how he would ask the 42-year-old beauty to be his wife and got down on bended knee at sunset in the palatial suite at the five-star hotel in Hawaii.

"He didn't want to propose in a public setting, even though there are so many beautiful spots on the hotel grounds that have spectacular views and are well-known as places where people pop the question. But Joe said he didn't want to risk anyone walking by and witnessing it, and he didn't want to tip off Sofia by having security there shooing people away."

The couple immediately toasted their engagement with champagne and "desserts were sent later on."

Sofia has a 22-year-old son, Manolo, from a previous marriage and ended her engagement to Nick Loeb in June.